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FXUS01 KWBC 290833
PMDSPD
SHORT RANGE FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD
433 AM EDT THU OCT 29 2009
VALID 12Z THU OCT 29 2009 - 00Z SAT OCT 31 2009
THE POWERFUL WEATHER SYSTEM CURRENTLY MOVING THROUGH THE CENTER OF
THE NATION IS THE HEADLINING STORY AS ITS EFFECTS COVER A
SIGNIFICANT PORTION OF THE U.S. CURRENTLY THE NATIONAL WEATHER
SERVICE HAZARDS CONSIST OF HEAVY SNOW RELATED WARNINGS UP AND DOWN
THE ROCKIES AND INTO THE NORTHERN HIGH PLAINS. THE OTHER ASPECT OF
THIS STORM IS THE HEAVY RAINFALL WHICH HAS RESULTED IN NUMEROUS
ISSUANCES OF FLASH FLOOD WATCHES CURRENTLY EXTENDING FROM
SOUTHEAST TEXAS NORTHEASTWARD INTO THE UPPER GREAT LAKES. WIND
WILL ALSO BECOME AN ISSUE...ESPECIALLY IN CLOSE PROXIMITY TO THE
SURFACE LOW CENTER AS IT QUICKLY STRENGTHENS ON ITS MOTION
NORTH-NORTHEASTWARD. IN ADDITION...IN THE WAKE OF THIS STRONG
UPPER-LEVEL TROUGH...BELOW NORMAL TEMPERATURES ACROSS THE DESERT
SOUTHWEST HAVE BROUGHT FREEZE WARNINGS INTO THE PICTURE FOR
CERTAIN LOCALES.
MORE HEAVY SNOW IS IN THE FORECAST ACROSS THE CENTRAL ROCKIES
TODAY BEFORE THE DISTURBANCE FINALLY EDGES EASTWARD BRINGING THE
HEAVIER ACTIVITY INTO SOUTH DAKOTA AND NEBRASKA. THIS SYSTEM
ALREADY HAS A HISTORY OF DROPPING HEAVY SNOW ACROSS EASTERN
COLORADO WITH WIDESPREAD TOTALS OF 2 TO 3 FEET WITH REPORTS OF
OVER A FOOT IN SOME OF THE LARGER CITIES LIKE BOULDER AND FORT
COLLINS. AS THE SYSTEM MOVES EASTWARD...SNOW WILL BECOME LESS OF
AN ISSUE AFTER THURSDAY WITH THE EXPECTED HEAVY RAINFALL BECOMING
A LARGER NUISANCE. THE FRONTAL BOUNDARY...WHICH CURRENTLY HAS OVER
3O TO 40 DEGREES OF GRADIENT ACROSS IT...WILL BE THE FOCUS FOR
VERY HEAVY PRECIPITATION. A SURGE OF GULF MOISTURE WILL INTERSECT
THE BOUNDARY WITH STRONG LIFT ALONG THE FRONT ALLOWING FOR THE
DEVELOPMENT OF HEAVY THUNDERSTORM ACTIVITY. THE BIGGEST CONCERN IS
THE SLOW MOVEMENT OF THE LINE OF STORMS WHICH HAS RESULTED IN
FLASH FLOOD CONCERNS ACROSS THE ARKLATEX AND INTO THE OZARKS
THROUGH FRIDAY MORNING. PLEASE VISIT THE HPC EXCESSIVE RAINFALL
FORECAST AT WWW.HPC.NCEP.NOAA.GOV/QPF/EXCESS_RAIN.SHTML FOR MORE
INFORMATION ON THE FLOODING IMPACTS.
THE OTHER AREA OF ACTIVE WEATHER TO CONCLUDE THE WORK WEEK IS OVER
THE PACIFIC NORTHWEST. A STRONG UPPER RIDGE WHICH HAS RESIDED OVER
THE EASTERN PACIFIC OCEAN WILL GRADUALLY BREAKDOWN AS A SERIES OF
TROUGHS DROP DOWN FROM THE GULF OF ALASKA. THE HEAVIEST FOCUS OF
PRECIPITATION WILL BE ACROSS WESTERN BRITISH COLUMBIA WHERE A 40
TO 45 KNOT SURFACE FLOW OFF THE PACIFIC WILL BRING TREMENDOUS
AMOUNTS OF MOISTURE INLAND...AND AGAINST THE LOCAL TERRAIN.
LIGHTER AMOUNTS CAN BE EXPECTED ACROSS THE NORTHWESTERN U.S. WITH
THE INTENSITY PICKING UP BY LATE FRIDAY. WHILE THE BIGGEST THREAT
WILL BE RAIN WITH THIS STORM...FREEZING RAIN CANNOT BE RULED OUT
ACROSS EASTERN WASHINGTON GIVEN FAVORABLE THERMODYNAMIC PROFILES
FOR THIS PRECIPITATION TYPE.
RUBIN-OSTER
GRAPHIC AVAILABLE AT WWW.HPC.NCEP.NOAA.GOV
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